PMDD... Determining Correct Dosage

D

Dopey

AC Members
Dec 5, 2002
92
0
6
Scranton, PA
Visit site
Hey all.

I've been having a nasty outbreak of hair algae subsequent to a tank break down and move about two months ago.

Tank is 90 gallons, heavily planted, presurrized C02 injection, 2x96w AH Supply lighting. Nitrogen, Nitrates, and phosphorus are zero. Plants grow well and bubble every night. (Unfortunately, so does the algae.)

I did not have a lot of water column feeding plants, but have gone out and bought quite a few to combat the problem. I've begun PMDD dosage at 1 tsp. per day. (I never fertilized the column before. Never had algae probelms.) Here's the issue. The algae continues.

How do I determine if I increase or decrease my initial dosage regimen of 1 tsp. Also, I am not dosing any iron such as Flourish or Florapride in the column... I only have laterite in the substrate. Could this be an issue?

How long do you think I should watch for the effects of a test regimen before changing. Would two weeks be sufficient?

Thanks.
 
PMDD dosing is a process based on the out of date papers of Sears Conlin I believe. The tanks were low tech then if I am not mistaken. It was an attempt to limit algae byt the limitation of phosphate. It doesn't work with higher light and CO2 addition for certain. What you will limit is the plant growth first. :) This means the algae will win the battle since they require so little supplementation. Take a look at the fertilizer sticky at the start of the forum for more information. I just dose the nutrients separately as they are needed since it's easier than figuring out some all purpose mix to use.
 
Saying out of date is a little harsh, no? The concept of PMDD and the Sears-Conlin paper is basically just that to control algea, you need to have a proper balance of nutrients. S-C suggested from their findings that algea seemed to be less when P was the limiting nutrient. That should hold true no matter what the setup. If you're adding more light, your nutrient requirement goes up. That means that if you don't add CO2, or aren't adding enough, C is going to be limiting instead of P. Likewise all the rest.

You will always need a good balance of nutrients and light. The beauty of PMDD is that you can adjust the makeup to suit your tank.
 
Could be a couple of things. Could be the laterite(I don't like the stuff). But this sounds like an example of root tabs or Jobes Sticks(don't like them either) getting into the water column when you moved. Is that a possibility?
If so, water changes, and lots of them is the answer, paying close attention to a light gravel vacuuming of the entire surface(where accessible).
You have only a bit over 2watts/gal., CF lighting in a fairly deep tank so a lot of fertilization is not going to be necessary.
If you could tell us exactly what you are dosing by breaking it down as to amounts of N/P/K it would help. A trace mix such as Flourish will be necessary, but in your case, as with all the nutrients, you won't have to go real heavy.
Tempest is right on with regard to PMDDs, IMO. Many of us don't use them, but rather opt to fertilize individual nutrients, at least until we know how much of each our individual tanks use.
And then the tanks(at least mine) are in a constant state of flux, so I'm constantly tweaking dosages. PMDD would never work for me.
The nutrient sticky will probably create a bunch more questions in your mind, but is a good starting point as to what many of us use and where to get it.

Len
 
Well, I don't think that it's anything stirred up from the substrate in the move. I did like a zillion water changes after re-setup.

Could a jobe's stick have gotten mixed up in the water colum afterwards, say while aquascaping.... yeah, that's possible.

I'm not dosing a lot of PMDD... but it's all I've ever used. I've never dosed individual nutrients except for iron.

I'm very, very confused after reading the sticky fertilizer thread. How in the world do you measure your nitrate, and phosphate and iron and carbon and potassium and magnesium all individually and decide which ones to adjust? I have a nitrate, phosphate test. But how do I measure carbon... with my Kh test? What about potassium, magnesium, and iron. Do these tests even exist? And if you get algae, how do you know if it's too much of X or too little of Y???? Is there a source that tells me how many ppm I should have of each?

I'm baffled. I've been keeping live plants succesfully for four years and all of a sudden feel like an amateur again.
 
When I did some aquascaping in my tank I really careful with the jobes sticks. When you pull them up they break into little pieces and float around in the water. I found using a gravel vacuum did a job of getting rid of any loose bit on the surface of the gravel or floating in the water.
 
Interesting.

By cross referencing the Fertilizing thread here, the Estimative Index article by Tom Barr, and the Calculator link from that article, we can find a lot of information.

However, Tom implies in his article that costly test kits aren't really vital, and that there is an estimative way to dose correctly (enough).

However, I've re-read the article four times now, and still am not getting the section entitled "The Estimative Part" which I gather is explaining why/how we estimate rather than test. Can someone try explaining this to me in other words? As near as I can tell, Tom is saying "just add some every week." I know I'm missing something.

Thanks
 
Originally posted by Dopey

However, I've re-read the article four times now, and still am not getting the section entitled "The Estimative Part" which I gather is explaining why/how we estimate rather than test. Can someone try explaining this to me in other words? As near as I can tell, Tom is saying "just add some every week." I know I'm missing something.

Thanks
Click to expand...

You don't just add "some," you add an amount that you know exactly. So, knowing how much you added, and the volume of your tank (the water, to be more specific), you can calculate exactly what the concentration is. Well, not exactly, but as good as a test kit will ever tell you. Play around with Chuck's calculator, and ask specific questions if you still can't get it. (remember, ppm = mg/L)
But don't miss the part about weekly water changes. If you don't do water changes and keep dosing the same every week, some stuff might build up.
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom